Total knee replacement (TKR) is effective in relieving pain and improving function in patients with severe osteoarthritis (OA) However, studies report that 14-30% of patients are dissatisfied with the result and do not achieve the expected benefits, especially in function. Objectives: To examine the factors influencing decision-making before TKR. Methods: We made a phenomenological study of the determinants that lead patients to accept, delay or reject TKR (this study is part of a larger study). Demographic and clinical data were collected and pain intensity measured by the WOMAC scale. Focus groups were conducted and the results transcribed and analysed using the 4-stage analysis of qualitative data according to Ritchie, Spencer and O'Connor (2003). Results: 12 patients (9 female, mean age 71.58 + 6.02 years, BMI 37.43 + 5.32, mean comorbidities 6.73 + 2.19 and mean WOMAC pain 14.9 + 8.89, function 15.77 + 8.6, total 15. 71 + 8. 22) were included: 6 had received, 4 were waiting for and 2 had rejected TKR. Focus groups identified widespread pain (pain intensity functional limitations), causal beliefs and perceptions (OA a natural process associated with age, obesity, physical work, sport) mood (importance of optimism), professional-user relationship (communication, experience of OA) expectations (need for surgery conditioned by pain, lost function, surgical risks), and social support (promotion of healthy habits and adherence conditioned by family and social support) as factors influencing attitudes to undergoing TKR. Conclusions: The process of deciding to undergo TKR is complex and influenced by multiple factors. TKR improves a small proportion of an aging painful body. Our results suggest the need of care before and after TKR, psychosocial support and preventive and educational programmes. References: Ritchie J, Spencer L, O'Connor W. Carrying out qualitative analysis. In Ritchie J. and Lewis J. (eds.) guide for social science students and researchers Oaks; New Delhi. Qualitative research practice: A. Sage: London; Thousand; 2003 Disclosure of Interest: None declared